Pipe thread lubricant stabilized with organic sulfides

ABSTRACT

PIPE THREAD LUBRICANTS COMPRISING MINERAL OIL, METAL DUST SELECTED FROM LEAD, ZINC, OR ALLOYS THEREOF, AND ALKALINE EARTH METAL SOAP AND CONTAINING A STABILIZING AMOUNT OF AN ORGANIC SULFIDE HAVING THE FORMULA R-SN-R1 WHEREIN R AND R1 ARE HYDROCARBON RADICALS OF 2 TO 20 CARBON ATOMS AND N IS AN INTEGER OF FROM 2 TO 4.

United States Patent 3,751,363 PIPE THREAD LUBRICANT STABILIZED WITHORGANIC SULFIDES Raymond Rohde and Marvin M. Johnson, Bartlesville,

Okla, assignors to Phillips Petroleum Company No Drawing. Filed Feb. 9,1971, Ser. No. 114,042 Int. Cl. C10m 5/16, 5/22 US. Cl. 252-19 6 ClaimsABSTRACT OF THE DISCLOSURE Pipe thread lubricants comprising mineraloil, metal dust selected from lead, zinc, or alloys thereof, andalkaline earth metal soap and containing a stabilizing amount of anorganic sulfide having the formula R--S,,R wherein R and R arehydrocarbon radicals of 2 to 20 carbon atoms and n is an integer of from2 to 4.

BACKGROUND OF THE INVENTION This invention relates to pipe threadlubricants. In one of its aspects, it relates to antigalling threadlubricants containing metal particulate dust. In another of its aspects,it relates to stabilizing metal-dust-containing lubricants againstreaction with water.

In one concept of the invention it relates to preventing thedecomposition of a metal-dust-containing, antigalling thread lubricantby addition of a stabilizing compound to the lubricant to preventreaction of the metal dust with Water.

In the drilling of deep wells in the oil and gas industries high torqueand elevated temperatures are encountered in the drilling operationswhich cause frequent problems of thread galling and joint seizure of thedrill piping. The drill piping is expensive and its recovery and reuseis es sential to an economic drilling operation. To increase theprobability of recovery of the drill piping an antigalling threadlubricant is used. Most pipe thread lubricants include one or morepowdered solids dispersed in various types of lubricating bases. Themost advantageous of these lubricants are mixtures of metallic dust inhigh temperature alkaline earth metal-based grease, such as a mixture ofzinc dust and a high temperature calcium-based grease.

Unfortunately exposure of a mixture of 'a metallic dust and a hightemperature alkaline earth-based grease to moisture during storage cancause a reaction which produces explosive mixtures of hydrogen, i.e.,zinc dust and water will react to produce hydrogen and zinc oxide.

Ruptures of containers resulting from the gas accumula tion duringstorage of this material have been reported repeatedly. Hydrogen gasexplosions are also a possibility and both phenomena may have takenplace simultaneously.

To avoid these hazards sulfur or nitrobenzene have been added to thistype lubricant as stabilizers. While these stabilizers reduce theproblem of hydrogen formation, other disadvantages have appeared.Nitrobenzene is a skin irritant continued exposure to which results inheadaches and nausea. The amount of sulfur necessary to prevent hydrogenformation causes a chemical reaction with the grease to produce productswhich are corrosive to the drill pipe.

It is therefore an object of this invention to provide a metallicdust-containing, antigall thread lubricant stabilized againstdecomposition by reaction with water. It is another object of thisinvention to provide a stabilized antigall thread lubricant that is freeof health hazards and metallurgical decomposition elfects. It is anotherobject of this invention to provide a means for stabilizing antigallthread lubricants.

Other aspects, concepts and objects of the invention are apparent from astudy of this disclosure and the appended claims.

SUMMARY OF THE INVENTION According to the present invention there isprovided a stable antigall thread lubricant based on a lubricatingcomposition of mineral oil, metallic dust, and an alkaline earth metalsoap to which is added a stabilizing amount of an organic sulfide havinga formula RS --R' wherein R and R are chosen from aliphatic and aromatichydrocarbon radicals of 2 to 20 carbon atoms, not necessarily identical,and n is an integer of from 2 to 4.

In one embodiment of the invention ditertiary butyl disulfide is addedas a stabilizer to a lubricant composition composed of mineral oil, zincdust, and a calcium soap to stabilize the lubricant againstdecomposition by reaction with water.

The base grease compositions used in this invention are the metallicdust containing lubricants well known for use in the industry. Thesegreases consist of a mineral oil or parafiin oil having a viscosity of100 to 120 SUS at 210 R; an alkaline earth metal soap, usually a calciumsoap; and a metallic lubricating dust, usually lead, zinc or alloysthereof.

The mineral oil usually makes up from 25 to percent by weight of thebase grease composition. A preferred composition for the base greasecontains from about 35 to about 55 percent by weight of mineral oilhaving a viscosity of to SUS at 210 F.

Any of the alkaline earth metal soaps can be used such as: alkalineearth metal salts of higher fatty acids having from l2-20 carbon atomssuch as oleic, stearic, palmitic, myristic, linoleic, dodecanoic acidsor mixtures thereof. Calcium stearate, calcium oleate, calciumpalmitate, magnesium stearate, magnesium palmitate, strontium linoleate,barium dodecanoate, barium stearate, among others or mixtures of thesemay be used. The alkaline earth metal soap preferred in the compositionof this invention is a calcium soap such as calcium stearate. Alkalineearth metal soap makes up from about 2 to about 10 percent by weight ofthe base grease composition and preferably is about 5 percent by weightof the base grease composition.

The metal dusts suitable for use in this invention include zinc, lead oralloys thereof, among others. Zinc is the preferred metal used as alubricating metal dust in the composition of this invention. Powder of aparticle size that will pass through a 200 mesh screen is advantageouslyused. The metal dust comprises from about 25 to about 75 percent byweight of the base grease composition and preferably will comprise inthe range of about 40 to about 60 weight percent of the base greasecomposition.

The base grease composition is prepared by thoroughly blending themineral oil, the metallic dust, and the alkaline earth metal soap. Suchblends are well known in the art and any of the usual methods forobtaining a homo geneous blend of the ingredients may be used.

The inhibiting compounds useful in this composition are organic sulfideshaving the formula RS R' where R and R are hydrocarbon radicals of 2 to20 carbon atoms. R and R can be the same or ditferent and can be alkyl,aryl, or aryl-alkyl. The inhibitor compound can contain up to 4 sulfuratoms. Mixtures of sulfides can also be used. The inhibitor is added tothe base grease formulation in amounts ranging from about 0.1 to about 5parts per hundred parts of the formulated base grease. A preferred rangefor the inhibitor addition is about 0.2 to about 1.5 parts per hundredparts of formulated base grease. The compounds suitable for use in thisinvention are, among others,

diethyl disulfide di-n-propyl disulfide di-tert-butyl disulfidedi-n-butyl disulfide di-tert-hexyl disulfide din-dodecyl disulfidedi-eicosyl disulfide ethyl-tert-bntyl disulfide di-phenyl 'disulfidetert-butyl hexyl polysulfide where n has an average value between 2.5and 3.5

di-tert-dodecyl polysulfide where n has an average value between 2.5 and3.5

di-tert-amyl polysulfide where n has an average value between 2.5 and3.5

di-tert-butyl polysulfide Where n has an average valuebetween 2.5 and3.5.

The following are specific examples showing a test procedure forevaluating the inhibiting qualities of various additives for thecomposition of this invention and the effectiveness of selectedadditives as stabilizers for this composition.

EXAMPLE I A base grease was prepared by thoroughly blending 40 parts byweight mineral oil having a viscosity of 100-120 SUS at 210 F., 55 partsby weight zinc dust and 5 parts by weight calcium soap to obtain ahomogeneous mixture. To this base grease was added 0.5 percent by weightof the compounds to be tested as inhibitors. The test inhibitors, whenadded, were thoroughly blended into the composition. The inhibitingcompounds tested are shown in Table I below.

EXAMPLE II Approximately 25 grams of a lubricating compound of Example Iwas sealed in a 4-inch pressure tube; a 20 ml. hypodermic syringeinserted through the top; and the i system (tube and syringe) flushedand blanketed with inert gas. The tube was immersed in a water bath at140 F. The hypodermic syringe served as a gas expansion chamber. Thetube remained in the water bath until gas evolution as measured bymovement of the plunger was maximum. If no. gas evolution occurred intwo weeks the test was discontinued. If gas evolved it peaked in 5 to 7days. The gas phase in the system consisting of inert blanket gas andgenerated gas was analyzed by gas chromatography to determine the amountof hydrogen that had been evolved.

The attached Table I summarizes the results obtained. Six tests wereconducted on the base pipe thread compound (uninhibited)+1 percent Waterand no additive. Four of the six tests gave sizable evolution ofhydrogen.

TABLE L-GAS ANALYSIS Composition of gas phase in bottle (mol percent)Zinc dust drilling compound uninhibited Gas Inert Hydroplus 1% H20evolved gas gen No additive None 99. 5 0. 5 Do. do 99. 3 0. 7 Do- Yes45. 55. 0 Do- Ye 52. 4 47. 6 Do. Yes 43. 0 57. 0 Do. Yes 44. 9 55. 1Plus 0.5% nitrobenzene N one 99. 6 0.4 0. do 99. 6 0. 4 Plus 0.5% (zincdithiophosphate) Yes--. 97. 8 2. 2 Yes 57. 0 43. 0 Plus 0.5% qninnnnNone 0 Yes 76. 3 22. 4 Plus 0.5% ditertiary butyl dlsulfide None. 99. 20. 8 Do. d o 99. 4 0. 6 Do (In Do do Do fin This table indicated thatthe production of hydrogen is quite likely when water is present withthe uninhibited lubricating compound, and that, although hydrogen can beproduced when a sulfide inhibitor is employed, the amount of hydrogenproduced is not suificient to be dangerous. This table also indicatesthe effectiveness of both nitrobenzene and ditertiary butyl disulfide asinhibitors of the reaction of the zinc dust and water according to thisinvention. As noted before nitrobenzene has noxious qualities which makeit undesirable as an additive in this type composition.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure, and the appended claims to the invention theessence of which is that organic sulfide compounds are effectivestabilizers to prevent the reaction of metallic dust and water inantigalling thread lubricants.

We claim:

1. A stable lubricating composition comprising (1) a formulated basegrease of mineral oil vehicle, an effective amount of a metal dustselected from the group consisting of lead, zinc, or alloys thereof, andalkaline earth metal soap thickener and (2) a stabilizing amount of anorganic sulfide having the formula RS -R' wherein R and R are chosenfrom aliphatic and aromatic hydrocarbon radicals having 2 to 20 carbonatoms, not necessarily identical, and n is an integer of from 2 to 4.

2. The composition of claim 1 comprising about 0. to about 5 parts oforganic sulfide per hundred parts of formulated base grease.

3. The composition of claim 1 wherein the formulated base grease iscomprised of about 25 to about percent by weight of a mineral oil havinga viscosity of to SUS at 210 F., about 75 to about 25 percent by weightof a metal dust; and about 2 to about 10 percent by weight of analkaline earth metal soap.

4. The composition of claim 3 wherein the metal dust is zinc, thealkaline earth metal soap is calcium soap, and the organic sulfide isditertiary butyl disulfide.

5. A method of inhibiting from reaction with water a lubricatingformulation comprising a formulated base grease of mineral oil vehicle,an effective amount of a metal dust selected from the group consistingof lead, zinc, and alloys thereof, and alkaline earth metal soapthickener by incorporating therein a stabilizing amount of an organicsulfide having the formula R-S -R', wherein R and R are chosen fromaliphatic and aromatic hydrocarbon radicals having 2 to 20 carbon atoms,not necessarily identical, and n is an integer of from 2 to 4.

6. The method of claim 5 wherein the organic sulfide is incorporatedinto the lubricating formulation in amounts in the range of about 0.1 toabout 5 parts per hundred parts of lubricating formulation.

References Cited UNITED STATES PATENTS 1,758,598 5/1930 Fritzell 2521-492,065,247 12/ 1936 Smith 25219 2,065,248 12/1936 Smith 252-l9 2,205,9906/1940 Nelson et a1 25219 2,211,373 8/1940 Folda 252-19 3,507,789 4/1970 Heilweil et a1 252-19 2,158,668 5/1939 Rosen 25246.4

DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner us. 01.X.R. 252-26, 406

